118 research outputs found
Transfer learning for radio galaxy classification
In the context of radio galaxy classification, most state-of-the-art neural
network algorithms have been focused on single survey data. The question of
whether these trained algorithms have cross-survey identification ability or
can be adapted to develop classification networks for future surveys is still
unclear. One possible solution to address this issue is transfer learning,
which re-uses elements of existing machine learning models for different
applications. Here we present radio galaxy classification based on a 13-layer
Deep Convolutional Neural Network (DCNN) using transfer learning methods
between different radio surveys. We find that our machine learning models
trained from a random initialization achieve accuracies comparable to those
found elsewhere in the literature. When using transfer learning methods, we
find that inheriting model weights pre-trained on FIRST images can boost model
performance when re-training on lower resolution NVSS data, but that inheriting
pre-trained model weights from NVSS and re-training on FIRST data impairs the
performance of the classifier. We consider the implication of these results in
the context of future radio surveys planned for next-generation radio
telescopes such as ASKAP, MeerKAT, and SKA1-MID
Radio Galaxy Zoo: Leveraging latent space representations from variational autoencoder
We propose to learn latent space representations of radio galaxies, and train
a very deep variational autoencoder (\protect\Verb+VDVAE+) on RGZ DR1, an
unlabeled dataset, to this end. We show that the encoded features can be
leveraged for downstream tasks such as classifying galaxies in labeled
datasets, and similarity search. Results show that the model is able to
reconstruct its given inputs, capturing the salient features of the latter. We
use the latent codes of galaxy images, from MiraBest Confident and FR-DEEP NVSS
datasets, to train various non-neural network classifiers. It is found that the
latter can differentiate FRI from FRII galaxies achieving \textit{accuracy}
, \textit{roc-auc} , \textit{specificity} and
\textit{recall} on MiraBest Confident dataset, comparable to results
obtained in previous studies. The performance of simple classifiers trained on
FR-DEEP NVSS data representations is on par with that of a deep learning
classifier (CNN based) trained on images in previous work, highlighting how
powerful the compressed information is. We successfully exploit the learned
representations to search for galaxies in a dataset that are semantically
similar to a query image belonging to a different dataset. Although generating
new galaxy images (e.g. for data augmentation) is not our primary objective, we
find that the \protect\Verb+VDVAE+ model is a relatively good emulator.
Finally, as a step toward detecting anomaly/novelty, a density estimator --
Masked Autoregressive Flow (\protect\Verb+MAF+) -- is trained on the latent
codes, such that the log-likelihood of data can be estimated. The downstream
tasks conducted in this work demonstrate the meaningfulness of the latent
codes.Comment: 21 pages, 13 figures, 2 table
Minimal linear codes from characteristic functions
Minimal linear codes have interesting applications in secret sharing schemes
and secure two-party computation. This paper uses characteristic functions of
some subsets of to construct minimal linear codes. By properties
of characteristic functions, we can obtain more minimal binary linear codes
from known minimal binary linear codes, which generalizes results of Ding et
al. [IEEE Trans. Inf. Theory, vol. 64, no. 10, pp. 6536-6545, 2018]. By
characteristic functions corresponding to some subspaces of , we
obtain many minimal linear codes, which generalizes results of [IEEE Trans.
Inf. Theory, vol. 64, no. 10, pp. 6536-6545, 2018] and [IEEE Trans. Inf.
Theory, vol. 65, no. 11, pp. 7067-7078, 2019]. Finally, we use characteristic
functions to present a characterization of minimal linear codes from the
defining set method and present a class of minimal linear codes
Representation Learning for Attributed Multiplex Heterogeneous Network
Network embedding (or graph embedding) has been widely used in many
real-world applications. However, existing methods mainly focus on networks
with single-typed nodes/edges and cannot scale well to handle large networks.
Many real-world networks consist of billions of nodes and edges of multiple
types, and each node is associated with different attributes. In this paper, we
formalize the problem of embedding learning for the Attributed Multiplex
Heterogeneous Network and propose a unified framework to address this problem.
The framework supports both transductive and inductive learning. We also give
the theoretical analysis of the proposed framework, showing its connection with
previous works and proving its better expressiveness. We conduct systematical
evaluations for the proposed framework on four different genres of challenging
datasets: Amazon, YouTube, Twitter, and Alibaba. Experimental results
demonstrate that with the learned embeddings from the proposed framework, we
can achieve statistically significant improvements (e.g., 5.99-28.23% lift by
F1 scores; p<<0.01, t-test) over previous state-of-the-art methods for link
prediction. The framework has also been successfully deployed on the
recommendation system of a worldwide leading e-commerce company, Alibaba Group.
Results of the offline A/B tests on product recommendation further confirm the
effectiveness and efficiency of the framework in practice.Comment: Accepted to KDD 2019. Website: https://sites.google.com/view/gatn
A model local interpretation routine for deep learning based radio galaxy classification
Radio galaxy morphological classification is one of the critical steps when
producing source catalogues for large-scale radio continuum surveys. While many
recent studies attempted to classify source radio morphology from survey image
data using deep learning algorithms (i.e., Convolutional Neural Networks), they
concentrated on model robustness most time. It is unclear whether a model
similarly makes predictions as radio astronomers did. In this work, we used
Local Interpretable Model-agnostic Explanation (LIME), an state-of-the-art
eXplainable Artificial Intelligence (XAI) technique to explain model prediction
behaviour and thus examine the hypothesis in a proof-of-concept manner. In what
follows, we describe how \textbf{LIME} generally works and early results about
how it helped explain predictions of a radio galaxy classification model using
this technique.Comment: 4 pages, 1 figure, accepted summary paper for URSI GASS 2023 J0
Radio Galaxy Zoo: The Distortion of Radio Galaxies by Galaxy Clusters
We study the impact of cluster environment on the morphology of a sample of
4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the
sample lies within a projected 15 Mpc of an optically identified cluster.
Brightest cluster galaxies (BCGs) are more likely than other cluster members to
be radio sources, and are also moderately bent. The surface density as a
function of separation from cluster center of non-BCG radio galaxies follows a
power law with index out to (Mpc), which
is steeper than the corresponding distribution for optically selected galaxies.
Non-BCG radio galaxies are statistically more bent the closer they are to the
cluster center. Within the inner (Mpc) of a cluster,
non-BCG radio galaxies are statistically more bent in high-mass clusters than
in low-mass clusters. Together, we find that non-BCG sources are statistically
more bent in environments that exert greater ram pressure. We use the
orientation of bent radio galaxies as an indicator of galaxy orbits and find
that they are preferentially in radial orbits. Away from clusters, there is a
large population of bent radio galaxies, limiting their use as cluster
locators; however, they are still located within statistically overdense
regions. We investigate the asymmetry in the tail length of sources that have
their tails aligned along the radius vector from the cluster center, and find
that the length of the inward-pointing tail is weakly suppressed for sources
close to the center of the cluster.Comment: 23 pages, 17 figures, 2 tables. Supplemental data files available in
The Astronomical Journal or contact autho
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